Enzyme rate and controlled measurements
הוצג| English | משמעות |
|---|---|
| enzyme/ˈenzaɪm/ | אנזים |
| denaturation/ˌdenətʃəˈreɪʃn/ | דנטורציה |
What would explain this observation?
- An enzyme 酶 works quickly at one temperature and slowly at another. Heating can increase successful collisions, but excessive heat can change the active site.
Build the model
- An enzyme is a biological catalyst.
- The substrate binds at an active site whose shape and chemical properties support the reaction.
- A catalyst increases rate without being used up overall.
- enzyme: A biological catalyst.
- denaturation 变性: A structural change that disrupts function.
Which change best tests the effect of pH?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Testing pH means changing only pH. Buffers of different pH at one fixed temperature isolate pH as the variable; changing temperature or enzyme concentration at the same time would mix two variables and the result could not be attributed to pH.
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Measure rate using product formed per unit time or a fixed endpoint.
- For an endpoint test, 1/time is a rate proxy if the same amount of product or substrate change defines the endpoint each time.
In the lab: For starch digestion, equilibrate enzyme and starch in a water bath, control pH with buffer, mix measured volumes, and test samples with iodine at fixed intervals. Use a clean spot for each test. Do not put iodine into the reaction mixture.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: the endpoint is reached in 40 s.
- Use rate proxy = 1/time.
- Rate proxy = 1/40 = 0.025 per second.
- At 20 s the proxy is 0.050 per second, twice as large.
- This comparison is valid only if the same endpoint and starting concentrations are used.
Your turn: A fixed endpoint takes 50 s. Calculate the rate proxy 1/time.
A fixed endpoint takes 50 s. Calculate the rate proxy 1/time.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 0.02 1/s. Known: the endpoint is reached in 50 s. Use rate proxy = 1/time. Rate proxy = 1/50 = 0.02 per second. This proxy is comparable with the 40 s worked case (0.025 per second) only because the same endpoint definition is used.
Check the conclusion and its limits
- An optimum is specific to the enzyme and conditions.
- Low temperature usually slows the reaction; it does not necessarily denature the enzyme.
- Endpoint intervals limit precision.
Not true: A low temperature always permanently denatures an enzyme. Low temperature usually only slows an enzyme because molecules collide less often; the active site is unchanged and warming restores activity. Denaturation is a structural change from excessive heat or extreme pH, not a guaranteed result of cooling.
- An enzyme is a biological catalyst.
- Measure rate using product formed per unit time or a fixed endpoint.
- Watch for: an optimum is specific to the enzyme and conditions.
Write from a rate proxy of 0.0125 per second
- A fixed endpoint takes 80 s.
- Find the rate proxy 1 over time. The same endpoint must define every trial.
Low temperature usually only slows an enzyme because molecules collide less often; the active site is unchanged and warming restores activity.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
True. Low temperature usually only slows an enzyme because molecules collide less often; the active site is unchanged and warming restores activity. Denaturation is a structural change from excessive heat or extreme pH, not a guaranteed result of cooling.
A biological catalyst: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
enzyme means A biological catalyst.
A fixed endpoint takes 80 s. What is the rate proxy 1 over time, and why must every trial use the same endpoint?
1 over 80 is 0.0125 per second. The proxy is not the amount of product.
What is the rate proxy?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
1 divided by 80 is 0.0125 per second. Other options — 0.020 per second (the earlier calculation's result for a 50 s endpoint); 0.025 per second (the lesson example's result for a 40 s endpoint).